Negative pressure air bearing

ABSTRACT

A negative-pressure air bearing slider structure includes a slider surface disposed adjacent to a data storage medium, and a leading edge relative to the motion of the data storage medium. A U-shaped rail with a closed end facing the leading edge and an open end facing the trailing edge is formed on the slider surface. The closed end of the U-shaped rail extends laterally across less than the width of the slider surface. In a first set of embodiments, there is a single U-shaped rail centered between two side rails. In a second set of embodiments, there are two U-shaped rails, each disposed along a respective side of the slider surface.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation-in-part application of application Ser. No.07/967,359, filed Oct. 28, 1992, now U.S. Pat. No. 5,438,467.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to computer data storage drives andmore specifically to a negative air pressure air bearing sliderstructure employed in conjunction with data storage drives.

2. Description of the Related Art

The negative pressure air bearing slider designs of the prior art aregenerally preferable to conventional flat taper slider configurations.The negative pressure structure enables the utilization of lowsuspension preloads, yielding decreased stationary frictional forces.These forces are oftentimes referred to as "stictional" forces. Negativepressure structures also offer the potential for improved stop/startperformance.

One shortcoming of state-of-the-art negative pressure air bearingdesigns is that the slider produces large negative loads. An example ofsuch a design is disclosed in the Warner et al. reference, U.S. Pat. No.4,475,135. These structures achieve a high air bearing stiffness whichimproves the compliance to the disk, but also increases the impactforces resulting from asperity and third-body contact. Such high-impactforces tend to degrade device reliability. Consequently, a structureoffering the ability to optimize the amount of stiffness or negativepressure would be desirable. Another drawback of the prior art negativepressure air bearing is its high skew sensitivity. For zone bitrecording applications, it is advantageous to maintain a constantspacing profile, but in rotary actuator file environments, the skewangle varies across the data band. Highly skew sensitive negativepressure designs experience high roll under these conditions resultingin a non-flat spacing profile. Thus, a negative pressure air bearingwhich is insensitive to skew would be desirable.

Although it is possible to adjust the amount of stiffness on existingslider structures by increasing the depth of the etched relief, thisapproach has significant drawbacks. Deepening the etched reliefincreases the fly height sensitivity of the slider structure.Furthermore, the reverse air current flow within the depths of theetched relief will be increased, thereby increasing the slider'spropensity to accumulate debris. Therefore, it would be desirable todevelop a technique for adjusting the negative pressure of the sliderstructure which is independent of the etch depth. It would also bedesirable to provide a means for flushing debris through and out of theair bearing. It would also be desirable to provide an air bearingstructure having improved static and dynamic performance over existingstructures.

SUMMARY OF THE INVENTION

The air bearing slider of the present invention provides a structurewhich optimizes the amount of negative pressure provided by the sliderstructure. This slider is employed in conjunction with a data storagemedium which may be engaged in motion relative to the slider. The sliderstructure includes a leading edge and a trailing edge, the edges beingdetermined with reference to the motion of the data storage medium. Theslider also includes a bottom surface which faces the data storagemedium. The bottom surface extends between the leading edge and thetrailing edge.

The negative pressure contours of the slider are determined by means ofa U-shaped rail situated between two outer taper-flat pads on the bottomsurface. The amount of negative pressure is controlled by adjusting thelength and width of the area enclosed by the U-shaped rail. The twoouter taper-flat pads provide roll stiffness. These pads may be extendedto the trailing edge of the slider to provide a mounting location for aread/write element. Skew insensitivity is achieved by adjusting therelative widths of the U-shaped rail and the outer taper flat pads. Thechannels formed between the U-shaped rail and the outer taper flat padsprovide a constant flow through the slider which flushes contamination.In this manner, the negative pressure contours may be optimized forspecific device applications.

A second embodiment of the invention includes an isolated islandpositioned between the legs of a U-shaped rail. The purpose of theisland is to provide means for mounting a read/write element to theslider. Two outer pads are employed for improving the roll stiffnesscharacteristics of the slider. These pads may be offset from thetrailing edge toward the leading edge of the slider to minimize rollsensitivity.

A third embodiment of the invention includes element mounting means inthe form of a center rail extending from the U-shaped rail to thetrailing edge of the slider structure. Two outer pads are employed,which may be offset from the trailing edge toward the leading edge ofthe slider to minimize roll sensitivity.

According to a fourth embodiment of the invention, the U-shaped rail canbe situated at a position on the bottom surface between the leading andtrailing edges of the slider structure. Centering the U-shaped railbetween the lateral edges of the slider provides enhanced pitch angleand fly height design flexibility.

In an alternative embodiment of the slider, two U-shaped rails arespaced laterally on the bottom surface near the slider leading edge.Independent adjustment of the area enclosed by each U-shaped rail, aswell as the relative widths of the inner and outer rails, providesenhanced skew insensitivity over previous embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features, aspects, and advantages of the present inventionwill become apparent from the following more particular descriptionthereof, presented in conjunction with the following drawings.

FIG. 1 is a perspective view illustrating the operational environment ofthe present invention in the context of a data storage drive mechanism.

FIG. 2 is a block diagram illustrating the operational environment ofthe present invention in the context of a data storage drive mechanism.

FIGS. 3A and 3B are bottom plan and rear elevation views, respectively,of a U-shaped rail air bearing slider structure according to a firstembodiment of the present invention.

FIG. 3C is a cross-sectional view taken along plans 3C--3C of FIG. 3A.

FIG. 3D is a cross-sectional view of an alternate embodiment of theslider structure of the present invention which employs a leading stepcompression feature instead of a taper.

FIG. 3E is a bottom plan view of a prior art slider without a U-shapedrail.

FIG. 3F is a cross-sectional view taken along plans 3F--3F of FIG. 3E.

FIG. 3G is a graph of pressure contours along the prior art slider.

FIG. 3H is a bottom plan view of a slider with a U-shaped rail adjacenta tapered leading edge.

FIG. 3I is a cross-sectional view taken along plans 3I--3I of FIG. 3H.

FIG. 3J is a graph of pressure contours along the slider of FIG. 3H.

FIGS. 4A and 4B are bottom plan and rear elevation views, respectively,of a U-shaped rail air bearing slider structure according to a secondembodiment of the present invention which includes an isolated islandpositioned between the side pads of the U-shaped rail.

FIGS. 5A and 5B are bottom plan and rear elevation views, respectively,of a U-shaped rail air bearing slider structure according to a thirdembodiment of the present invention which includes load bearing meansand a center rail attached to the U-shaped rail.

FIGS. 6A and 6B are bottom plan and rear elevation views, respectively,of a U-shaped rail air bearing slider structure according to a fourthembodiment of the present invention in which a curved portion of theU-shaped rail is positioned near the center of the first surface of theslider structure.

FIGS. 7A-7B are bottom plan and rear elevation views, respectively, ofan alternate embodiment of the slider structure of the present inventionwhich employs two U-shaped rails separated by a center rail.

FIGS. 8A and 8B are bottom and rear elevation views, respectively, of aslider structure similar to that of FIGS. 7A and 7B, but wherein outsiderails have been adapted to support a read/write element.

FIGS. 9A-9D illustrate bottom plan views of various prior-art sliderconfigurations and a U-shaped rail air bearing slider according to theinvention.

FIG. 10 graphically illustrates the magnitude of negative air pressureversus velocity for the slider structures shown in FIGS. 9A, 9B and 9D.

FIG. 11 graphically illustrates the magnitude of negative air pressureversus velocity for two slider structures according to the invention.

FIG. 12 graphically illustrates velocity versus flying height for theslider structures shown in FIGS. 5A and 5B, 7A and 7B, and 9C.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS THE INDUSTRIALENVIRONMENT

FIG. 1 is a perspective view illustrating means for employing thepresent invention in a direct access storage device (DASD). In thisregard, the invention concerns a slider 10 which is supported in a DASDwith respect to a disk surface 12 by a slider suspension assembly 14which includes a mount plate 16 and load beam 18. The slider 10 isattached to the load beam 18 by means of a flexure 19. A data read/writetransducer 20 is mounted on the slider 10. One or more leads 21 connectthe transducer 20 to DASD electronics.

FIG. 2 is a block diagram illustrating the essential complement offunctional components in a DASD employing the slider design of thisinvention. Although FIG. 2 illustrates a single-disk device, it is to beunderstood that this is not intended to limit the practice of theinvention to such devices. In fact, the invention is applicable as wellto DASD's with multiple disks.

In FIG. 2 the disk 30 is mounted on a rotatable spindle 32 that isrotated by a drive motor 33. The disk 30 has an upper surface 34 and alower surface 35. A slider 38 with a transducer mounted thereon facesthe upper surface 34. Another slider 40 with a transducer mountedthereon faces the lower surface 35. The sliders 38 and 40 are positionedwith respect to these surfaces 34 and 36 by respective movable sliderarm assemblies 45 and 46. The arm assemblies are conventionally mountedto an actuator 42. The transducers on the sliders 38 and 40 areconnected to conventional data channel electronics. In FIG. 2 read/writechannel electronics 48 are shown only for the slider 38, it beingunderstood that the transducer on the slider 40 is similarly supportedin the DASD. A control unit 50, typically in the form of a processor,provides position control signals on a signal path 52 to the actuator42. These signals control the positions of the slider 38 and 40 withrespect to the surfaces of the disk 30. The control unit 50 providesmotor speed control signals to control the rotational speed of the drivemotor 33. The control unit 50 also processes read and write signals forthe transducer on the slider 38 by way of the read/write channelelectronics 48.

Each slider 38 and 40 may support one or more read/write transducers. Asthe disk 30 rotates, the sliders 38 and 40 are moved radially in and outover their respective disk surfaces so that the read/write transducersmay access different portions of the disk 30 where desired data isrecorded. Each slider 38 and 40 is attached to a respective actuator arm45 and 46 by means of a suspension mechanism.

During operation of the DASD, the rotation of the disk 30 forces airbetween each of the sliders 38 and 40 and its respective disk surface bymeans of a progressive elevation feature, typically a taper or a seriesof one or more steps defined on the slider surface. This cushion of air(an "air bearing") exerts an upward force against a slider, whichcounterbalances an opposing disk-directed force exerted on the slider.The balance of forces supports a slider off of a disk by small,substantially constant spacing ("flying height") during operation. Innegative-pressure sliders, the upward force is exerted againstspaced-apart taper-flat slider rails; the opposing force is exerted by arecessed area on the slider surface between the rails which creates asuction acting between the slider and the disk surface. The balancebetween the forces results in a very slight positive load on the slider,while the rails provide a very stiff bearing.

The flying height of a slider is the distance between a particular pointon a slider and the disk surface when the slider is supported on itscushion of air. Typically, the slider point coincides with a transducerlocation; usually, this location is at the trailing edge of the slider.It should also be noted that the terms "spacing" and "slider spacing"when used in the description and drawings are synonymous with flyingheight.

THE INVENTION

FIGS. 3A and 3B illustrate bottom plan and rear elevation views,respectively, of a U-shaped rail air bearing slider structure 100 inaccordance with a first embodiment of the present invention. The sliderstructure 100 is designed to be used in a data storage device having astorage medium engaged in motion relative to the slider during dataread/write operations. The slider structure includes a supportingsurface 101 which, in the industrial environment, is positioned adjacentto and facing the data storage medium. The U-shaped rail 102 ispositioned between two outer taper-flat rails 104 and 105, each of whichextend outwardly from supporting surface 101 by offset height 125. Anintermediate surface 124 may be enclosed by the U-shaped rail 102, andis offset from supporting surface 101 by offset height 123. Theintermediate surface 124 is in turn offset from an air bearing surfaceof the U-shaped rail 102 by offset height 122. The rails 104 and 105include respective forward tapers 106 and 107. The slider structure 100has a leading edge 110, a trailing edge 111, and respective side edges112 and 113. The U-shaped rail 102 includes a cross rail portion 114which transitions to a forward tapered section 115. As shown in FIG. 3A,the cross rail portion 114 extends laterally across less than the fullwidth of the slider structure 100 between the side rails 104 and 105.The U-shaped rail 102 also includes a pair of side rails 116 and 117which are substantially parallel with the forward sections of the siderails 104 and 105 and which join the cross rail portion 114 to form athree-sided enclosure enclosing an area 118 on the intermediate surface124. Flow through channels 120 and 121 are formed between side rail 116and taper flat rail 104, and side rail 117 and taper flat rail 105,respectively. FIG. 3C illustrates a cross sectional view of slider 100in FIG. 3A through the centerline of U-shaped rail 102. Cross railportion 114, side rail 116 and outer taper flat rail 104 extend fromsupporting surface 101 by offset height 125. Intermediate surface 124 isoffset from supporting surface 101 by offset height 123, and is offsetfrom the bottom surface of cross rail 114 by offset height 122. Tapersection 115 extends forward and angles downward from cross rail 114.FIG. 3D shows a cross-sectional view of an alternative embodiment of thepresent invention where step 126 is located adjacent to cross rail 114.The bottom surfaces of the rails 104 and 105, the cross rail 114 and theside rails 116 and 117 provide an air bearing surface (ABS).

During operation, the slider structure is supported on an air bearingbetween the ABS and the rotating disk 30. Air is compressed by one ormore progressive elevation features and forced under the slidergenerating a negative pressure force in area 118 enclosed on three sidesby the U-shaped rail 102. Progressive elevation features may consist oftapers 106, 107, and 115, a series of one or more steps 126, or anyother combination of tapers and steps. A lifting force is generated byair compressed by tapered portions 106 and 107, and the outer pads 104and 105. Negative pressure is generated by air compressed by the taperedportion 115 and cross bar 114 and then subsequent expansion into area118. In order for air expansion to occur, cross bar 114 must be offsetfrom intermediate surface 124 by offset height 122. This is explained inFIGS. 3E-3J. FIG. 3E shows a prior art slider with a U-shaped rail wherethe crossbar is fully contained within the taper portion. There is nooffset height between the crossbar and the bottom surface as illustratedin FIG. 3F. The resulting pressure profile is shown in FIG. 3G. Contour1 is the positive pressure produced by the outer taper flat side rails.Contour 2 shows the pressure produced along the center of the U-shapedrail at section 3F--3F. Note this pressure is positive and near ambientas the air is only slightly compressed and not permitted to expand. Butthe slider with U-shaped rail shown in FIG. 3H provides an area for thisexpansion. FIG. 3I illustrates a crossbar with an offset height from thesupporting surface. The pressure contours generated by this geometry areshown in FIG. 3J. Once again, contour 1 is the positive pressureproduced by the outer taper flat side rails, and contour 2 shows thepressure produced along the centerline of the U-shaped rail. Initiallypositive pressure is generated as the air is compressed by the taper andcrossbar. But then the air expands as it flows past the crossbar andinto the offset portion of the bottom surface, creating the subambientnegative pressure shown by contour 2. The suction force produced by thisnegative pressure is substantially larger than the added lift forcecreated by the added area of the crossbar, such that the slider in FIG.3H actually flies lower than the slider in FIG. 3E. Without offsetheight 122, negative pressure will not be generated. The amount ofnegative air pressure generated by the slider structure 100 iscontrolled by the length and width of the area 118.

The two outer taper-flat rails 104 and 105 are each situatedsubstantially adjacent to a respective side edge. These rails provideroll stiffness and may be extended to the rear surface 108 to provide amounting location for read/write transducers. As FIG. 3A illustrates,the rails 104 and 105 have substantially constant widths from theleading edge 110 to the tips of the rails 116 and 117. From there to thetrailing edge 111, the widths of the pads 104 and 105 increaseconstantly. Channels 120 and 121 provide a path for air flow through thelength of the slider for continuous flushing of contamination anddebris. Intermediate surface 124 bounded by U-shaped rail 102 is offsetfrom supporting surface 101 by offset height 123 to facilitate debrisremoval from the slider, as well as further constrain the negativepressure generation to area 118. Offset height 123 may be varied or eveneliminated completely according to design requirements. In thisinstance, surfaces 101 and 124 would lie in a common plane. Skewinsensitivity is achieved by adjusting the relative lengths and widthsof side rails 116, 117 and the widths of outer rails 104, 105. Adjustingthe widths of these rails changes the amount of positive pressure liftforce generated by the slider. Independently, the relative lengths ofside rails of the U-shaped pocket 116 and 117 adjust the amount ofnegative pressure generated. By balancing the positive and negativepressure as a function of skew angle, a constant fly height is achieved.

As shown in FIG. 3A (and in the embodiments illustrated in FIGS. 4A, 5Aand 6A), the U-shaped rail is formed on the bottom surface of the sliderat a location which is centered between, but separated from the siderails. This structure characterizes the first through the fourthembodiments of the invention.

FIGS. 4A and 4B are bottom plan and rear elevation views, respectively,of a U-shaped rail air bearing slider structure 200 in accordance with asecond embodiment of the invention. The slider structure 200 correspondsessentially to the slider structure 100 of FIGS. 3A and 3B in having aU-shaped rail 202 with a forward taper 203 that extends outwardly fromthe sup-porting surface 201 and is centered laterally between two outertaper-flat rails 204 and 205 with forward tapers 206 and 207,respectively. Unlike the earlier embodiment of the invention shown inFIG. 3A, an intermediate surface is not shown offset from supportingsurface 201 in region 213 bounded by U-shaped rail 202, as illustratedin FIG. 4A. Moreover, unlike the taper-flat rails 104 and 105 of FIG.3A, the taper-flat rails 204 and 205 in FIG. 4A exhibit a continuouswidth. However, the outer taper-flat rails 204 and 205 do not extendalong the full length of the bottom surface 201 from leading edge 210 totrailing edge 211. Rather, the rails 204 and 205 are offset from thetrailing edge 211 to minimize roll sensitivity. An isolated island 212is provided on the supporting surface 201 at a position which abuts thetrailing edge 211 and is centered between the legs of the U-shaped rail202. This island provides a site at which a data read/write transduceris mounted.

FIGS. 5A and 5B illustrate bottom plan and rear elevation views,respectively, of a U-shaped rail air bearing slider structure 300 inaccordance with the third embodiment of the present invention. Theslider structure 300 is essentially identical with the slider structure200 illustrated in FIGS. 4A and 4B with exception that it does notinclude an isolated island. Rather, the slider structure in FIGS. 5A and5B includes a center rail 310 which is adapted to carry a dataread/write transducer at the trailing edge 311. The center rail 310extends from the vertex 313 of the U-shaped rail 302 to the trailingedge 311 of the slider structure 300. The width of the center rail 310increases continuously from the vertex 313 to the trailing edge 311. Thecenter rail provides added lift force and improved pitch stability.

FIGS. 6A and 6B illustrate bottom plan and rear elevation views,respectively, of a U-shaped rail air bearing slider structure 400 inaccordance with a fourth embodiment of the present invention. The sliderstructure 400 corresponds essentially to the slider structure 300 ofFIGS. 5A and 5B. In this regard, the slider structure 400 includes onits supporting surface 401 a U-shaped rail 402. However, the rail 402includes a forward edge 403 without an adjacent progressive elevationfeature and is offset from the leading edge 410 of the slider structurein the direction of the trailing edge 411. This slider structureincludes a center rail 410 which extends, with a constantly-increasingwidth, from the vertex 413 of the U-shaped rail 402 to the trailing edge411. Positioning the U-shaped rail 402 in this manner provides a sliderstructure having desirable pitch angle and flying height properties.Although the crossbar does not utilize a progressive elevation feature,air still compresses over the crossbar and expands into the U-shapedarea generating a negative pressure.

FIGS. 7A and 7B are bottom plan and rear elevation views, respectively,of an alternate embodiment of the slider structure of the presentinvention which employs two U-shaped rails separated by a center rail.In this alternate embodiment, the slider structure 1300 has two U-shapedrails 1301 and 1303 separated by a center rail 1305, these railsextending from the supporting surface 1320 of the slider. Rails 1301 and1303 include forward tapered sections 1302 and 1304, respectively. Thecenter rail 1305 includes a forward tapered section 1306. The U-shapedrail 1301 includes outer and inner rails 1307 and 1311, respectively,while the rail 1303 includes outer and inner rails 1309 and 1313,respectively. Although the outer rails 1307 and 1309 are illustrated asbeing longer and wider than the inner rails 1311 and 1313, the relativedimensions of length and width may be varied according to designrequirements. The widths and lengths of the inner rails 1311 and 1313may be wider and/or longer than the outer rails 1301 and 1303. The outerrails are positioned adjacent respective side edges of the slider toprovide roll stiffness and to maintain the slider structure in arelatively high pitch angle. The length of the inner rails 1311 and 1313and the width of the U-shaped rails 1301 and 1303 at the rail vertices1315 and 1317, respectively, may be optimized for specific values ofnegative loading. Each of the U-shaped rails 1301 and 1303 may bealtered independently, allowing the slider 1300 to be optimized forspecific roll conditions and/or rotary skew environments. Either or bothof the U-shaped pockets 1301 and 1303 may enclose an intermediatesurface offset between supporting surface 1320 and the bottom surfacesof the U-shaped pockets 1301 and 1303, similar to surface 124 of theembodiment shown in FIG. 3A. Use of this intermediate surface allows forimproved debris insensitivity and further localization and control ofthe generated negative pressure. The skew insensitivity of this geometryis enhanced by the added flexibility of adjusting the relative lengthsand widths of rails 1301, 1303, 1311 and 1313 to balance the positiveand negative pressure generated by two U-shaped rails, thus achieving aconstant fly height.

FIGS. 8A and 8B illustrate bottom plan and rear elevation views,respectively, of a U-shaped rail air bearing slider structure 1400 whichis essentially equivalent to the slider structure 1300 of FIGS. 7A and7B. In this regard, the slider 1400 includes two U-shaped rails 1401 and1404, respectively, which extend from the supporting surface 1420 of theslider. The U-shaped rail 1401 includes an outer rail 1407 adjacent afirst side edge of the slider, which extends to the trailing edge 1411of the slider 1400 and a shorter inner rail 1411. Similarly, theU-shaped rail 1403 includes an outer rail 1409 adjacent a second sideedge of the slider and extending to the trailing edge 1411, and arelatively shorter inner rail 1413. The extension of the outer rails1407 and 1409 to the trailing edge 1411 adapts them for supporting dataread/write elements. This eliminates the need for a center rail in theslider structure 1400. Again, adjusting the relative lengths and widthsof rails 1411 and 1413 as well as the widths of 1407 and 1409 canachieve constant fly height by balancing the positive and negativepressures as a function of skew angle.

FIGS. 9A-9D illustrate plan views for several air bearing sliderstructures, including various prior-art slider structures and a U-shapedair bearing rail structure according to the present invention. Theslider structure of the third embodiment of the invention is illustratedin FIG. 9D. This slider structure 300 is identical to the structureshown in FIG. 5, and may hereinafter be referred to as the "Embodimentthree" slider 300.

FIGS. 9A and 9B show prior-art negative-pressure slider structures,referred to as the Prior Art "A" slider 1501, and the Prior Art "B"slider 1502, respectively. The Prior Art "A" slider 1501 and the PriorArt "B" slider 1502 are less advantageous than the Embodiment threeslider 300 shown in FIG. 9D. FIG. 9C illustrates a slider structure ofthe prior art, which is very similar to the positively loaded tri-rail,taper-flat structure commonly in use in presently-existing data storagedrives. This prior-art slider structure is included in the presentanalysis for purposes of comparison only, and may be referred to as thePrior Art "C" slider 1504.

FIG. 10 is a graph showing negative loading versus velocity for theEmbodiment three slider 300, the Prior Art "A" slider 1501, and thePrior Art "B" slider 1502. The test conditions reproduced conditions ofthe industrial environment illustrated in FIG. 1. In this regard, eachslider was mounted to a suspension assembly and maintained thereby overa rotating disk. Standard modelling techniques were used to determinethe negative loading produced by each slider in response to diskvelocity. Referring to the graph of FIG. 10, the Embodiment three slider300 exhibits relatively low negative loading as compared to the priorart slider designs. The Embodiment three slider 300 also exhibitsadjustable negative pressure independent of flying height and railetching depth. The design has relatively low sensitivity to fabricationtolerances and low sensitivity to data accessing skew. Improved dampingis provided, as well as relatively fast take-off from the data storagemedium surface.

FIGS. 11 and 12 provide graphical comparisons between the operation ofthe alternative embodiment slider 1300 and the Embodiment three slider300. The comparison of FIG. 12 also considers the performance of aconventional Prior Art "C" slider 1504 (FIG. 9C).

The comparisons illustrated in FIGS. 11 and 12 were conducted usingsmall sliders which measured 1.6 mm in width×2.5 mm in length. Theresulting bottom surface area of the slider 1300 was 12% less than theslider 300 with the consequence that the slider 1300 provided improvedstationary friction properties. Both the slider 1300 and the slider 300utilized suspension loads of approximately 1 to 2 grams, which was fourtimes less than the suspension loaded needed for the Prior Art "C"slider 1504. This reduction in suspension loads leads to superiorstart/stop performance and further reduces stiction.

The graph of FIG. 11 illustrates the low negative pressure achievablefor two negative-pressure slider designs of the invention; namely, theslider 1300 and the slider 300.

The graph of FIG. 12 shows minimum flying height versus velocity for thePrior Art "C" slider 1504, the slider 300, and the slider 1300. Theslider 1300 of the present invention takes off just as fast from thedata storage medium surface as the slider 300, and much faster than thecontrol Prior Art "C" slider 1504. The high take-off velocity is acharacteristic shared by negative-pressure slider designs.

With reference to FIGS. 7A-7B, 11 and 12, the slider 1300 has advantagesover presently-existing air bearing slider designs. The slider 1300generates low negative pressure independent of etch depth and flyingheight. This slider also exhibits reduced sensitivity to manufacturingtolerances, and improved performance during the data storage mediumaccess operations. Furthermore, the slider features rapid take-off fromthe surface of the data storage medium, constant flying height in rotaryactuator skew environments and flow through channels for contaminationflushing.

A number of specific embodiments of the present invention have beendescribed. Nevertheless, it will be understood that variousmodifications and changes may be made without departing from the spiritand scope of the invention. As an example, each of the tapers of thetaper flat side rails adjacent the side edges of the sliders shown inFIGS. 3-6 and the taper flat of the center rail of the slider shown inFIG. 7A can be stepped with one or more steps as shown at 126 and 114 inFIG. 3D instead of being a taper. This same modification can be made tothe tapers of the cross rails of the U-shaped rails of the sliders shownin FIGS. 4, 5, 7 and 8. Further, the step at 403 in FIG. 6A can be amultiple step, as shown in FIG. 3D, or a taper, as shown in FIG. 3C.Another modification is to provide an offset as shown at 123 in FIG. 3Cfor each of the areas enclosed by the U-shaped rails in FIGS. 4-8.Accordingly, it is to be understood that the invention is not to belimited by the specific illustrated embodiments, but only by the scopeof the appended claims.

We claim:
 1. A slider for supporting a transducer in relation to amoving data storage medium, comprising:a slider structure with a leadingedge, a trailing edge, and first and second side edges; a bottom surfacebounded by said leading, trailing and side edges; a first U-shaped railon and projecting outwardly from said bottom surface, said firstU-shaped rail including:a cross rail substantially parallel with saidleading edge and extending across less than one-half a width of saidbottom surface; the cross rail having a taper-flat which includes ataper portion and a flat portion; the taper portion of the cross railand the leading edge of the slider being parallel with respect to oneanother and the taper portion tapering in height from the flat portiontoward the leading edge of the slider; a first side rail substantiallyperpendicular to and adjoining said cross rail, said first side railsubstantially adjacent and parallel to the first side edge and extendingfrom said cross rail towards said trailing edge; a second side rail,substantially parallel to said first side rail and offset from saidfirst side rail toward the center of said bottom surface; the secondside rail being shorter than the first side rail; and a second U-shapedrail projecting outwardly from said bottom surface, said second U-shapedrail including:a cross rail substantially parallel with said leadingedge and extending across less than one-half a width of said bottomsurface; the cross rail having a taper-flat which includes a taperportion and a flat portion; the taper portion of the cross rail and theleading edge of the slider being parallel with respect to one anotherand the taper portion tapering in height from the flat portion towardthe leading edge of the slider; and a first side rail substantiallyperpendicular to and adjoining said cross rail, said first side railsubstantially adjacent and parallel to the second side edge andextending from said cross rail towards said trailing edge; a second siderail, substantially parallel to said first side rail and offset fromsaid first side rail toward the center of said bottom surface; and thesecond side rail being shorter than the first side rail,whereby, uponmoving said data storage medium adjacent the slider, the rails of thefirst and second U-shaped rails produce positive pressures and areaswithin the U-shaped rails produce negative pressures which are dependentupon the shortness of said second side rails.
 2. A data storage driveincluding the slider of claim 1, the drive comprising:the movable datastorage medium; means for moving the movable data storage medium; andmeans for supporting the slider adjacent the movable data storagemedium.
 3. A slider as claimed in claim 1 including:the flat portion ofthe cross rail and the first and second side rails of the first andsecond U-shaped rails having surfaces which lie in a common plane forproducing said negative pressures.
 4. A slider as claimed in claim 3including:the tapered portion of each cross rail being adjacent saidleading edge of the slider.
 5. An air bearing slider for use with a datastorage drive having a movable storage medium, said air bearing sliderincluding:a slider body having a supporting surface which is bounded byleading and trailing edges and a pair of side edges, the supportingsurface being adapted for facing the movable storage medium; and firstand second U-shaped rails on said supporting surface, each U-shaped railincluding:a cross rail projecting from said supporting surface, andsubstantially parallel with said leading edge and extending across lessthan a full width of said supporting surface as defined by the sideedges; the cross rail having a progressive elevation portion and a flatportion; the progressive elevation portion of the cross rail and theleading edge of the slider being parallel with respect to one anotherand the progressive elevation portion decreasing in height from the flatportion toward the leading edge of the slider; first and second siderails projecting from said supporting surface, each of said side railsextending from said cross rail in the direction of said trailing edge;the second side rail being shorter in its extension from said cross railin the direction of the trailing edge than the extension of the firstside rail in its extension from the cross rail in the direction of thetrailing edge; and the first side rail of the first U-shaped rail beingimmediately adjacent one of said side edges and the first side rail ofthe second U-shaped rail being immediately adjacent the other side edge.6. The air bearing slider of claim 5 including:each of said side railsextending from the cross rail to a respective point offset from saidtrailing edge.
 7. An air bearing slider for use with a data storagedrive having a movable storage medium, said air bearing sliderincluding:a slider body having a supporting surface which is bounded byleading and trailing edges and a pair of side edges, the supportingsurface being adapted for facing the movable storage medium; and firstand second U-shaped rails on said supporting surface, each U-shaped railincluding:a cross rail projecting from said supporting surface, andsubstantially parallel with said leading edge and extending across lessthan a full width of said supporting surface as defined by the sideedges; the cross rail having a progressive elevation portion and a flatportion; the progressive elevation portion of the cross rail and theleading edge of the slider being parallel with respect to one anotherand the progressive elevation portion decreasing in height from the flatportion toward the leading edge of the slider; first and second siderails projecting from said supporting surface, each of said side railsextending from said cross rail in the direction of said trailing edge;the second side rail being shorter in its extension from said cross railin the direction of the trailing edge than the extension of the firstside rail in its extension from the cross rail in the direction of thetrailing edge; and the progressive elevation portion of the cross railbeing adjacent to and extends along the leading edge; the first siderail being positioned adjacent a respective side edge of the slider, andthe second side rail being positioned parallel to the first side rail,but offset from the first side rail toward an opposite side edge of theslider; and the cross rail of one of said U-shaped rails being spacedfrom the cross rail of the other U-shaped rail.
 8. The air bearingslider of claim 7 including:the progressive elevation portion being astepped elevation.
 9. The air bearing slider of claim 7 including:theprogressive elevation portion being a taper.
 10. The air bearing sliderof claim 7 including:each of said first and second side rails having asurface which projects from the supporting surface which defines an airbearing surface; and each of said U-shaped rails enclosing an area whichhas an intermediate surface which is intermediate the supporting surfaceand the air bearing surface.
 11. The air bearing slider of claim 7including:each of said first and second side rails having a surfacewhich projects from the supporting surface which defines an air bearingsurface; and each of said U-shaped rails enclosing an area which has asurface which is coplanar with the supporting surface.
 12. The airbearing slider of claim 11 including:the progressive elevation portionbeing a taper.
 13. The air bearing slider of claim 7, wherein the firstside rail of at least one U-shaped rail extends from the leading edge tothe trailing edge.
 14. The air bearing slider of claim 7, wherein thefirst side rail of each U-shaped rail extends to a point offset from thetrailing edge, the air bearing slider further including a taper-flatcenter rail centered between said two U-shaped rails on said supportingsurface and extending from said leading edge to said trailing edge. 15.An air-bearing slider for use with a data storage drive having a movablemedium, said air-bearing slider comprising:a slider body having an airbearing surface which projects from a supporting surface and islocatable adjacent the movable storage medium, the supporting surfacebeing bounded by leading and trailing edges and first and second sideedges; two U-shaped rails on said supporting surface and projectingtherefrom, each U-shaped rail including:an elongated cross rail having alength along a longitudinal axis, the longitudinal axis of the crossrail and the leading edge of the slider being substantially parallelwith respect to one another and the length of the cross rail extendingacross less than a width of the slider as defined between the slider'sfirst and second side edges; the cross rail having an elongated tapersurface portion and an elongated flat surface portion, each of the tapersurface portion and the flat surface portion having a longitudinal axiswhich extends substantially parallel to the leading edge of the slider;the taper surface portion of the cross rail being located adjacent tothe flat surface portion of the cross rail and sloping from the flatsurface portion toward the leading edge of the slider and toward a planedefined by the supporting surface; first and second side railsinterconnected by the cross rail, each side rail having a flat surfacewhich extends from the flat surface portion of the cross rail toward thetrailing edge of the slider; the second side rail being shorter than thefirst side rail; the taper surface portion of the cross rail beingadjacent the leading edge of the slider; the flat surface portion of thecross rail and the flat surface of each one of said side rails lyingsubstantially in a common plane which forms at least a portion of theair bearing surface of the slider; the first side rail being positionedadjacent a respective side edge of the slider, and the second side railbeing positioned parallel to the first side rail, but being offset fromthe first side rail towards an opposite side edge of the slider; and thecross rail of one of said U-shaped rails being spaced from the crossrail of the other U-shaped rail.
 16. An air bearing slider as claimed inclaim 15 comprising:only the supporting surface of the slider and theair bearing surface of the slider facing the movable storage medium whenthe air bearing surface is located adjacent the movable storage medium.17. An air bearing slider as claimed in claim 15 comprising:the firstside rail of at least one U-shaped rail extending from the respectivecross rail to the trailing edge of the slider.
 18. An air bearing slideras claimed in claim 15 comprising:the second side rail of each U-shapedrail extending to a point offset from the trailing edge of the slider;and a taper-flat center rail centered between said two U-shaped rails onsaid bottom surface and extending from said leading edge to saidtrailing edge of the slider.